Cidofovir selectivity is based on the different response of normal and cancer cells to DNA damage

Abstract

BackgroundCidofovir (CDV) proved efficacious in treatment of human papillomaviruses (HPVs) hyperplasias. Antiproliferative effects of CDV have been associated with apoptosis induction, S-phase accumulation, and increased levels of tumor suppressor proteins. However, the molecular mechanisms for the selectivity and antitumor activity of CDV against HPV-transformed cells remain unexplained.MethodsWe evaluated CDV drug metabolism and incorporation into cellular DNA, in addition to whole genome gene expression profiling by means of microarrays in two HPV+ cervical carcinoma cells, HPV- immortalized keratinocytes, and normal keratinocytes.ResultsDetermination of the metabolism and drug incorporation of CDV into genomic DNA demonstrated a higher rate of drug incorporation in HPV+ tumor cells and immortalized keratinocytes compared to normal keratinocytes. Gene expression profiling clearly showed distinct and specific drug effects in the cell types investigated. Although an effect on inflammatory response was seen in all cell types, different pathways were identified in normal keratinocytes compared to immortalized keratinocytes and HPV+ tumor cells. Notably, Rho GTPase pathways, LXR/RXR pathways, and acute phase response signaling were exclusively activated in immortalized cells. CDV exposed normal keratinocytes displayed activated cell cycle regulation upon DNA damage signaling to allow DNA repair via homologous recombination, resulting in genomic stability and survival. Although CDV induced cell cycle arrest in HPV- immortalized cells, DNA repair was not activated in these cells. In contrast, HPV+ cells lacked cell cycle regulation, leading to genomic instability and eventually apoptosis.ConclusionsTaken together, our data provide novel insights into the mechanism of action of CDV and its selectivity for HPV-transformed cells. The proposed mechanism suggests that this selectivity is based on the inability of HPV+ cells to respond to DNA damage, rather than on a direct anti-HPV effect. Since cell cycle control is deregulated by the viral oncoproteins E6 and E7 in HPV+ cells, these cells are more susceptible to DNA damage than normal keratinocytes. Our findings underline the therapeutic potential of CDV for HPV-associated malignancies as well as other neoplasias.

Insights into the mechanism of action of cidofovir and other acyclic nucleoside phosphonates against polyoma- and papillomaviruses and non-viral induced neoplasia

“…Recently, we reported that following 72 h incubation with CDV, CDVp-choline appeared to be the most abundant metabolite while the monophosphate form was the least abundant one in PHKs as well as in HPV-positive and HPV-negative tumor cells (De Schutter et al, 2013c). Importantly, no significant differences in the levels of the active metabolite CDVpp, CDVp-choline or CDV were observed between PHKs and HPV-positive tumor cells.…”

“…Since then, the family Papovaviridae is obsolete and the Papillomaviridae and Polyomaviridae families were recognized by the International Committee on Taxonomy of Viruses (ICTV) (Johne et al, 2011;de Villiers et al, 2004). Table 2 summarizes the main similarities and differences between PyVs and PVs.…”

“…Because it was later recognized that the two virus groups differ in several features such as genome sizes, genome organizations, and no major nucleotide or amino acid sequence similarities exist, they are now officially recognized by the International Committee on the Taxonomy of Viruses (ICTV) as two separate families, Papillomaviridae and Polyomaviridae (de Villiers et al, 2004).…”

Brincidofovir (CMX001) Inhibits BK Polyomavirus Replication in Primary Human Urothelial Cells

“…Another possible explanation for a stronger cytostatic effect in infected than uninfected cells could be that the DNA damage response is dysregulated in polyomavirus-infected cells (reviewed in reference 47). Analogous to this, primary keratinocytes with an intact DNA damage response were protected from CDV incorporation, while cancer cells failed to respond to DNA damage and incorporated more CDV (37). The viability of HUCs was much less affected than DNA replication by BCV, indicating that quiescent cells, such as the terminally differentiated umbrella cells of the urothelium, may tolerate BCV well.…”

“…Given the lack of a known virus-selective target for CDV in the polyomavirus proteome, the inherent genotoxic properties of CDV (37,38), and our observations of decreased cell numbers, it was thought pertinent to characterize the cytostatic and cytotoxic effects in some detail.…”